In the field of flow control systems, one technique for providing chilled process water to a plurality of remotes sites is to use a primary flow loop from chillers to the sites where the water is to be utilized, as for air cooling, and then back to the chillers for recyling in a continuous cycle of operation. At the remote sites where the process water is to be used, secondary flow loops tap from, and return to, the primary loop, the chilled water for use in air cooling at each of the various sites. As a result, there is one primary loop in a continuous flow and a plurality of secondary loops for utilizing the water from the primary loop as needed.
In considering any one secondary loop, there will be a section of crossover line which is common with both the primary loop and the secondary loop. The apparatus coupling the primary loop with a secondary loop is a water bridge. A primary pump is used to continuously feed the water through the primary loop. A secondary pump is used to feed the water through each secondary loop but only at a given rate and only when required. Without appropriate controls, however, the system would be very inefficient, chilling and/or feeding more or less water than is needed for the intended air cooling.
In U.S. Pat. No. 3,729,051, the problem of controlling the quantity of flowing water was addressed and solved. According to that patent, a small supplemental water line is placed across the common extent of the primary and each secondary loop. The supplemental line at each secondary loop was of a significantly smaller diameter for a limited flow, merely sufficient to sense a primary flow balance between the primary loop and the flow of the secondary loop.
For optimum efficiency, the flow through the primary loop should equal the flow through the total of secondary loops. If insufficient water is pumped in either loop, the intended cooling will not be effected. If excess water is pumped, unnecessary energy will be expended in moving the water. By sensing the flow along the supplemental line, verification may be made that water is flowing and that pressure exists in the suplemental line. So long as the sensed water in the supplemental line remains at the optimum predetermined flow, no change is made to the fluid flow. If, however, the sensed water varies from the predetermined flow, a signal is sent back to a first control valve in the primary loop to restrict the flow and thereby minimize the work done by the pump of the primary loop. This effects a greater efficiency.
In a subsequent improvement, as described in the U.S. Pat. No. 3,875,995, temperature as well as flow is taken into account for controlling water flow. In the event that the water in the secondary loop varies from its intended, predetermined temperature, inefficiency results. If the temperature of the water in the secondary loop is not cool enough, the intended air cooling will not be effected. If the temperature of the water in the secondary loop is too cool, excess chilling is being done at an unnecessary cost to the system and its user. As a result, a temperature control sensor is provided. So long as the sensed temperature is at a predetermined value, the chilling simply continues. If, however, the temperature deviates from the predetermined value, the difference is sensed and a signal is sent to a second control valve located in the crossover line of the water bridge to vary the quantity of chilled water provided to the secondary loop. This feature further increases the efficiency of the system.
In a third improvement to fluid control systems, as described in the copyrighted BRDG-TNDR Corporation brochure of 1988, the signals generated for temperature and flow control are fed back from the water bridges of the air cooling subassemblies to the water chiller subassembly to vary the amount of recirculating water being fed through the chiller to thereby modify the temperature and flow of the water in the primary loop. By keeping the water in the primary loop at a preselected temperature and flow for a particular application further efficiencies are effected in the system.
A fourth improvement is disclosed in U.S. patent application Ser. No. 464,346 filed Jan. 12, 1990. In its simplest terms, such fourth improvement is an improvement over prior flow control systems in that the temperature and flow sensors are replaced with electronic sensors of a size and capability more efficient than those previously know and utilized. Their use in the lines of fluid flow, as described above, not only generate more accurate readings but have less effect on the flow. This further increases the accuracy of readings and provides greater control and efficiency in the system. In addition, each temperature sensor is removed from the site of sensing and repositioned with its controller adjacent to its controlled valve. As such, all electronic controls for each secondary loop are integrated into a common controller for greater overall efficiency. This more readily allows all the controllers for all the secondary loops to be in two-way communication with a common host computer for integration of the system generally. As such, the efficiencies effected to the system are greater than the sum of the efficiencies of the individual water bridges.
As referred to above, the prior art discloses systems for controlling the flow of process fluids. Nothing in the prior art, however, controls the flow with the accuracy and efficiency afforded by the present invention.
Accordingly, it is an object of this invention to provide a method and apparatus which overcomes the aforementioned shortcomings and which is a significant contribution to the advancement of the arts.
It is a further object of the invention to provide a method and apparatus for coupling a primary and secondary loop for circulating processing fluids therebetween comprising a first connection for the feed line of the primary loop, a second connection for the return line of the primary loop, a third connection for the feed line of the secondary loop and a fourth connection for the return line of the secondary loop; a crossover line coupling the four connections; first valve means with a first sensor means responsive to the flow across the crossover line to control the first valve means; second valve means with a second sensor means responsive to the temperature of the process fluid in the secondary loop to control the second valve means; a common microprocessor for the first and second sensor means to control the first and second valve means as a function of the sensed flow and temperature; and a computer asociated with each secondary loop operable in response to the temperature associated with load fluid adjacent to its associated secondary loop to control the common microprocessor for each secondary loop.
It is a further object of this invention to provide controllers/sensors with two-way communications for the purpose of talking with a host computer and data acquisition equipment to thereby allow for control reset, control limits, systems management, trending, historical data accumulation, etc., based upon the property of the of air being processed.
A further object of the present invention is to monitor the fluid temperatures before and after being processed for the purpose of resetting flow and temperature set points to thereby control the flow of processing fluid.
The foregoing has outlined some of the more pertinent objects of the invention. These objects should be construed to be merely illustrative of some of the more prominent features and applications of the intended invention. Many other beneficial results can be attained by applying the disclosed invention in a different manner or by modifying the invention within the scope of the disclosure. Accordingly, other objects and a fuller understanding of the invention may be had by referring to the summary of the invention and the detailed description of the preferred embodiment in addition to the scope of the invention defined by the claims taken in conjunction with the accompanying drawings.